Public safety access point (PSAP) selection for E911 wireless callers in a GSM type system

ABSTRACT

Public safety access points are selected in a wireless network for E911 calls based on ESRD substitution when ESRKs are not being used. The present invention was conceived as an ESRK workaround solution to implement Phase II of the E911 rules from the starting point of a Phase I implementation. ESRKs, ESRDs or ESRVs are initially obtained and managed for each PSAP in a particular carrier&#39;s area. Then, Phase I processes are modified to wait to see if Phase II GSM location information will be reported in a timely manner (e.g., within a second or two or so) before committing to a default selection of a particular PSAP based on information available (e.g., based on the location of a serving cell site).

This application claims priority from U.S. Provisional PatentApplication No. 60/367,706, filed Mar. 28, 2002, entitled “HybridGSM/ISUP,” the entirety of which is expressly incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to wireless and long distance carriers,Internet service providers (ISPs), and information content deliveryservices/providers and long distance carriers. More particularly, itrelates to location services for the wireless industry, particularly forE-9-1-1.

2. Background of Related Art

When you dial 911, the call is directed to an assigned local PublicSafety Access Point (PSAP). The PSAP picks up the call along with aninbound telephone number or Automatic Number Identification (ANI)information. This number is used to query an Automatic LocationIdentification (ALI) database, match it with the corresponding addressas a location of the caller, and forward the location information andinbound telephone number to the assigned PSAP. The PSAP can then deliverboth the number and the location to the appropriate emergency service(fire, police and ambulance) so that the emergency response unit canproceed to the appropriate location.

This above scenario works well when the 911 call originates from aresidence, since every residential number is associated with a uniqueresidential address. However, for wireless devices which are highlymobile, exact location information is critical in determining thecorrect PSAP to be used.

E911 is short for Enhanced 911, a location technology advanced by theFCC that will enable mobile, or cellular, phones to process 911emergency calls and enable emergency services to locate the geographicposition of the caller. When a person makes a 911 call using atraditional phone with ground wires, the call is routed to the nearestpublic safety answering point (PSAP) that then distributes the emergencycall to the proper services. The PSAP receives the caller's phone numberand the exact location of the phone from which the call was made. Priorto 1996, 911 callers using a mobile phone would have to access theirservice providers in order to get verification of subscription servicebefore the call was routed to a PSAP. In 1996 the FCC ruled that a 911call must go directly to the PSAP without receiving verification ofservice from a specific cellular service provider. The call must behandled by any available service carrier even if it is not the cellularphone customer's specific carrier. Under the FCC's rules, all mobilephones manufactured for sale in the United States after Feb. 13, 2000,that are capable of operating in an analog mode must include thisspecial method for processing 911 calls.

The FCC has rolled out E911 in two phases. In 1998, Phase I requiredthat mobile phone carriers identify the originating call's phone numberand the location of the signal tower, or cell, accurate to within amile. Phase I of the FCC's E911 rules requires that a 7, 8 or 10 digitnumber accompany each 911 call, which allows the PSAP dispatcher toeither call back if the call is disconnected or to obtain additionalinformation such as the mobile's callback number. It also gives thedispatcher the location at the cell site that received the call as arough indication of the caller's location.

In 2001, Phase II required that each mobile phone company doing businessin the United States must offer handset- or network-based locationdetection capability so that the caller's location is determined by thegeographic location of the cellular phone within 100 meter accuracy—notmerely to the location of the tower that is transmitting its signal. TheFCC refers to this as Automatic Location Identification (ALI). Phase IIof the FCC's wireless 911 rules allows the dispatcher to know moreprecisely where the caller is located.

Advances in technologies that employ new or upgraded handsets havedemonstrated significant progress. However, as a practical matter,current FCC rules permit only network-based (i.e., independent ofhandset type) solutions to meet the Phase II requirements in the shortterm. As a result, the current rule effectively precludes use of ahandset-based (i.e., GPS-assisted or other interaction dependent on thehandset) approach, which needs to gradually replace or upgrade currenthandsets. Thus, in September 1999, the FCC revised its rules to permitthe phase-in of new or upgraded handsets in order for handset-basedsolutions to be a viable competitor for initial ALI deployment underPhase II, while making other revisions aimed at promoting wireless E911and improving public safety.

As can be appreciated, PSAP assigned regions do not correspond to cellsite coverage areas. Many cell sectors' RF coverage crosses state andcounty borders between PSAPs, but a wireless carrier is only able toconfigure their wireless switches regardless of the number of PSAPregions covered (i.e., as in Phase I requirements) to route to only asingle PSAP per cell sector.

Prior to Phase II implementation, it is possible that a small percentageof 911 dialers will be routed to an improper PSAP. This is because thecall is routed based on the particular cell site that was used tocommunicate, rather than to the correct PSAP assigned to a caller'slocation. In such an instance, wireless E911 calls would require atransfer between PSAPs (usually performed manually by personnel at theincorrect PSAP) because the geographic location of the caller did notcorrespond to the first PSAP dispatcher's jurisdiction.

J-STD-036 provides a protocol for non-GSM wireless systems to select thecorrect PSAP based on the caller's precise location, and has thecapability to greatly reduce the number of E911 calls that must betransferred between PSAPs (thus speeding up service). However, GSMsystems do not have a similar solution for PSAP routing based on thecaller's location only for routing based on the particular cell towerused by the caller.

Currently, in non-GSM systems, a selective router switch is used toselect the correct PSAP based on receipt of an ISUPGenericDigitsParameter that contains emergency service routing digits(ESRD). An ESRD is a 10 digit routable, but not necessarily dialablenumber that is used for routing to a PSAP—but only on a per originationcell sector basis. Thus, the ESRD helps a selective router route a callto the particular PSAP assigned to the cell sector serving the 911caller, causing the occasional need for manual or other type transfer ofthe PSAP caller.

A new ISUP CallingGeodeticLocation (CGL) parameter was defined in April2000 to help a selective router select the appropriate PSAP based on thecaller's precise location, not based only on the location of the servingcell tower, but this technology requires a software upgrade (e.g., tothe ISDN User Part (ISUP) software) at many switches, thus deterring anyemergence of this type solution. In fact, this particular technology maynever appear since non-GSM wireless switches already utilize an existingprotocol (J-STD-036) to determine PSAP selection prior to routing out ofthe wireless switch and it is only GSM wireless switches that would beserved by this type of solution.

There is a need for an apparatus and technology to provide improved PSAPselection to reduce the need for transfers between PSAPs, andconsequently to allow help to arrive for a wireless 911 caller that muchsooner.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention, a method ofproviding ESRK, ESRD or ESRV information for a wireless E911 callercomprises requesting accurate location information relating to thewireless E911 caller. The selection of a public safety access point isdelayed a given amount of time until the requested accurate locationinformation is received. A location relating to a serving base stationis returned as a default condition in place of the requested accuratelocation information if the accurate location information is notreceived before expiration of the given amount of time.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention will become apparent tothose skilled in the art from the following description with referenceto the drawings, in which:

FIG. 1 shows an ISUP/GSM logical diagram, in accordance with theprinciples of the present invention.

FIG. 2 shows an exemplary step for a mobile device caller to dial anemergency number (e.g., “9-1-1” in North America, “1-1-2” in Europe,etc.) shown in FIG. 1.

FIG. 3 shows exemplary steps for a cell tower to route an emergency callto an appropriate switch, as shown in FIG. 1.

FIG. 4 shows exemplary steps of a switch routing a call via an IAMmessage, as shown in FIG. 1.

FIG. 5 shows exemplary steps of an ISUP handler receiving an IAMmessage, as shown in FIG. 1.

FIG. 6 shows exemplary steps of staging an initial call record [CSS], asshown in FIG. 1.

FIG. 7 shows exemplary steps of a MAP subscriber location report messagereceived from a switch (i.e., an MSC), as shown in FIG. 1.

FIG. 8 shows exemplary steps of obtaining ESZ and of assigning an ESRK,as shown in FIG. 1.

FIG. 9 shows exemplary steps of staging updated data in an MPC's activecall record with latitude and longitude (lat/lon), as shown in FIG. 1.

FIG. 10 shows exemplary steps of a wireless network gateway providingrouting for an emergency call with IAM2, as shown in FIG. 1.

FIGS. 11A and 11B summarize the exemplary ISUP/GSM location processshown and described in FIGS. 1-10.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention allows for PSAP selection based on ESRDsubstitution when ESRKs are not used. When ESRD substitution is used forPSAP selection, the caller's serving cell sector ESRD can be deliveredafter call setup on, e.g., an NCAS data link. Moreover, with the presentinvention, the wireless operator need not be the entity required toobtain ESRKs and otherwise work with PSAPs. Instead, this task can bedelegated to an outside node, perhaps provided by a third party. WithESRD substitution, it is possible to replace all ESRKs for a PSAP anduse a single substituted ESRD per PSAP. A single substituted ESRD ismost cost effective, and is known as Emergency Services Routing Value(ESRV).

As is known, GSM is a European standard for telephone systems importedto North America. Currently, Europe does not have anything like E911implemented, or if they do, the implementations do not include multiplejurisdictions like city, county and state.

The present invention was conceived as an ESRK workaround solution toimplement Phase II of the E911 rules from the starting point of a PhaseI implementation. ESRK is a 10-digit routable, but not necessarilydialable, number that is used not only for routing but also as acorrelator, or key for mating of data that is provided to a PSAP bydifferent paths, such as via a voice path and via an automatic locationidentification (ALI) path. In daily use, the term ESRK is often used todistinguish operational environments where the “routing” digits areassigned on a per destination PSAP basis as opposed to a per originationcell sector basis (which is the strict technical definition).

One possible GSM non-standard solution for Phase II involves ISUPloop-around technology to a GSM carrier. However, the relevant J-STD-036standard lacks in many respects and places a burden on GSM wirelessswitch vendors who are generally unfamiliar with the vulgarities of E911call setup routing in North America.

Accordingly, in accordance with the principles of the present invention,ESRKs or ESRVs are initially obtained and managed for each PSAP in aparticular carrier's area. Also, importantly, Phase I processes aremodified to wait to see if Phase II GSM location information will bereported in a timely manner (e.g., within a second or two or so) beforeresorting to the selection of a particular PSAP based on otherinformation available (e.g., based on the location of a serving cellsite).

FIG. 1 shows an ISUP/GSM logical diagram, in accordance with theprinciples of the present invention. The elements of FIG. 1 will bedescribed with reference to FIGS. 2-11, which explain the signalingbetween the elements.

FIG. 2 shows an exemplary step for a mobile device caller to dial anemergency number (e.g., “9-1-1” in North America, “1-1-2” in Europe,etc.) shown in FIG. 1.

In particular, as shown in FIG. 2, the step 1 shown in FIG. 1 isassociated with a wireless caller dialing 9-1-1 (i.e., placing an E911call). It is presumed for the purposes of the disclosed embodiment thatthe mobile station used by the wireless caller is PCS1900 compatible.

FIG. 3 shows exemplary steps for a cell tower to route an emergency callto an appropriate switch, as shown in FIG. 1.

In particular, step 1.1 shown in FIG. 3 represents a cell tower routingan emergency call to the appropriate PSAP. In sub-step A of 1.1, themobile switching center (MSC) knows the cell tower's unique 10-digitESRD.

In sub-step B, the cell tower's control channel sends a setup messagewith dialed digits and an identifier for the E911 caller's mobilestation.

In sub-step C, the MSC knows the MSISDN and IMSI based on the MSidentifier.

FIG. 4 shows step 1.2 shown in FIG. 1, wherein a switch routes a callvia an IAM message. In sub-step A, the switch is provisioned for allemergency calls to route to the GMLC or MPC/GMLC ISUP point code for theISUP handlers. In sub-step B, the switch assigns the call's dialeddigits, MSISDN and ESRD to ISUP loop-around IAM's CalledPartyNumber,CallingPartyNumber and GDP, respectively.

FIG. 5 shows step 2 shown in FIG. 1, wherein an ISUP handler receives anIAM message. In sub-step A, the ISUP handler checks the switch profilefor the cell site indicated by the GDP=ESRD and that indicates “routingbased on position”. In sub-step B, the system supports a staticallypre-configured timer (T1) to wait for the incoming SubLocRpt messagewhen “routing based on position”. In sub-step C, the configurable timestarts as soon as the IAM1 is received. In sub-step D, if the timerexpires before the SubLocRpt for this call is received, then MPC willproceed with “routing based on cell sector”, otherwise known as ESRD.

In accordance with the principles of the present invention, GSM Phase Iwireless E911 loop-around technology is combined with the Phase IIJ-STD-036 standard for PCS1900, aka North American GSM. Moreover, andimportantly, the PSAP selection and the Phase I loop-around routing outof the GSM switch are delayed to see if a Phase II precise locationbecomes available for routing based on the E911 caller's location (i.e.,position). To avoid dead time in an emergency E911 call, a configurabletimer may be implemented. The timer is started during the call'srouting. Then, if the configurable timer expires before any location forthe E911 caller is obtained, routing based on cell sector (i.e.,reverting back to Phase I requirements) can proceed by default.

FIG. 6 shows step 2.1 shown in FIG. 1, wherein an initial call record[CSS] is staged. In sub-step A, an initial call record is created withparameters from the IAM1 message (CSS) ESRD maps to pre-provisionedinformation about the cell tower MSISDN maps from theCallingPartyNumber. In sub-step B, the timer T1 continues to run untilit either expires or the MAP Subscriber Location Report is received forthe call.

FIG. 7 shows step 2.2 shown in FIG. 1, wherein a MAP subscriber locationreport message is received from a switch (i.e., an MSC). In sub-step A,a MAP Subscriber Location Report Invoke message indicates that therelevant call is the origination of a new emergency call. Exemplary datatransmitted in this sub-step includes, but is not limited to, Callorigination, MSISDN (i.e., a dialable or non-dialable callback numberthat matches the IAM1's CallingPartyNumber), latitude/longitude of thecalling party's mobile device, LCS Client ID, MSC number, ESRD (whichmatches the IAM1's GDP) and usually an IMSI.

In sub-step B of step 2.2 shown in FIG. 7, aMAP_Subscriber_Location_Report message includes optional parameters thatare preferably included if available. Exemplary optional parametersinclude, e.g., the age (or time stamp) of any included location estimateof the caller, and/or any supplementary emergency services information(e.g., patient information). Additional message parameters maycorrespond to those documented in the standards J-STD-036 Chapter 6 andGSM 09.02.

Sub-step C relates to error parameters for the MPC/GMLC's response to anunacceptable MAP_Subscriber_Location_Report. These errors indicate anerror in the invoke message or in the MPC/GMLC that prevents thelocation related information from being accepted. The followingexemplary error types are allowed in the disclosed embodiment: “systemfailure”, “data missing”, and “unexpected data value”, or similarinformation.

FIG. 8 shows step 2.3 shown in FIG. 1, wherein the emergency serviceszone (ESZ) is obtained and the ESRK is assigned. In sub-step A, the CRDBmust be provisioned with appropriate emergency services zone informationfor latitude and longitude.

In sub-step B, the MPC/GMLC associates incoming latitude/longitudelocation or presence information for the caller's mobile station to thecorrect emergency services zone and PSAP as provisioned in the CRDB.

In sub-step C of FIG. 8, the MPC/GMLC is able to associate the emergencyservices zone with an appropriate ESRK from a pool of ESRKs for thecall.

In sub-step D, the MPC/GMLC provides a unique ESRK for the call (ifthere is one available). The ESRK is unique in that it is unique to anyactive call at any given time. The ESRKs may and will be reused overtime. If all maintained ESRKs are in use, the MPC/GMLC will use the ESRKfrom the “oldest” active call.

In sub-step E, the MPC/GMLC preferably immediately marks the ESRK as “inuse” to avoid (if possible) duplicate calls using the same ESRK.

FIG. 9 shows step 2.4 shown in FIG. 1, wherein updated data is staged inan MPC/GMLC's active call record with latitude and longitude (lat/lon).In sub-step A, updated call data is matched with the existing activecall record created by IAM1 using MSISDN from SubLocRpt.

In sub-step B, the following parameters are preferably staged as aresult of receiving the SubLocRpt Invoke message: ESRK;latitude/longitude of the caller's mobile device; location estimate;location accuracy (e.g., including inner radius, uncertainty radius,offset and included angle); and age of estimate, time stamp or othertime-based information related to the location determination.

In sub-step C, the second timer T2 is initiated upon receipt of IAM1ends information, when updated call data is staged. In sub-step D,staged call data is made available for retrieval by the system until thecall is released. In sub-step E, failure conditions may be reached,e.g., if for some reason posting in the CallData table fails, in whichcase an error record would be written. Also, if ESRD, MSISDN orlatitude/longitude information of the caller's mobile device are missingfrom the originating message, data should not be posted and an errormessage result should be returned to the requesting MSC.

FIG. 10 shows step 3 shown in FIG. 1, wherein a wireless network gatewayprovides routing for an emergency call with IAM2. In sub-step A, preciserouting is accomplished. In particular, the system causes the MSC toroute each E911 call to the best PSAP based on a SubLocRep locationestimate, if the SubLocRep location estimate is available for thatcaller within a statically pre-configured time interval (based on thefirst timer T1 as described herein).

In sub-step B, the PSAP is determined based on the fallback of cell sitesector identification. For a particular cell site, if the SubLocReplocation estimate is not available within the statically pre-configuredtime interval T1, then the MPC/GMLC causes the MSC to route that callbased on the identity of the cell site currently serving the caller (andthe PSAP assigned to that cell site).

In sub-step C, default routing is fallen back on. For a particular call,if neither the SubLocRep location estimate is available for the caller,nor the identity of the cell site sector, within the pre-configured timeinterval T1, the system causes the MSC to route that call to apre-configured default assigned PSAP.

In sub-step D, a MAP subscriber location report response is generated,including parameters such as call origination.

In steps 3.1 and 3.2 of FIG. 1, the MSC receives the IAM2 and tandemsthe call to the PSTN with IAM3.

FIGS. 11A and 11B summarize the exemplary ISUP/GSM location processshown and described in FIGS. 1-10, in accordance with the principles ofthe present invention. FIGS. 11A and 11B are shown in parallel since thereception of SubLocRep is parallel to the ISUP Handler process.

In particular, as shown in step 802 of FIG. 11B, the wireless callerdials 911 on a mobile device (i.e., an E911 caller).

In step 804, the cell tower routes the emergency call to the appropriateswitch.

In step 806, the switch routes the call via the IAM message.

In step 808, the ISUP handler receives the IAM message.

In step 810, the initial call record [CSS] is staged.

In step 812, the MAP Subscriber Location Report message is received fromthe switch (i.e., from the mobile switching center (MSC)).

In step 814, the emergency services zone (ESZ) is obtained, and a uniqueESRK is assigned.

In step 816, updated location data is staged, e.g., in an MPC's activecall record. Preferably the location data includes latitude andlongitude information.

In step 818, a gateway provides routing for the emergency E911 call withIAM2 messaging.

Thus, in accordance with the principles of the present invention, theprecise location that is obtained with existing location determiningequipment can be used to query a coordinates routing database (CRDB)where the E911 PSAP (or a pizza delivery area for a non-E911application, etc.) can be selected based on the latitude and longitudecoordinates of the wireless caller before the call is routed out of theGSM switch. This means the wireless carrier is able to control thedestination selection without dependence on another carrier such as theLEC. Current GSM standards do not describe the sequence of steps thatcoordinate the protocol necessary for location determining equipment tointeract with routing decisions at a GSM switch.

When common channel signaling and ISDN are available to setup the voicepath between the relevant wireless switch and assigned PSAP, CallAssociated Signaling (CAS) is capable of delivering a full twenty digitsto the PSAP's call display when the E911 call is answered. Ten (10) ofthese digits are the caller's callback number and another ten (10)digits are an ESRD that represents the caller's serving cell sector. TheESRD or substituted ESRD (i.e., ESRV) may be used by the selectiverouter to choose the assigned PSAP and it may also be used by the PSAPto obtain an address for the cell sector. In the ESRV case, it can helpthe PSAP determine where to get the actual serving call sector. Thesetwenty (20) digits are considered to be required for “Phase I” E911wireless channel associated signaling (CAS) service.

FCC Order number 98-xxxx requires “Phase II” E911 wireless service toalso provide the caller's location within 125 meters 95% of the time.Common channel signaling standards have added a new CGL parameter andthe T1-628-2000 standard was revised to define the mapping of an E911caller's latitude and longitude into the ISUP CGL parameter. Thisparameter is transferred into the ISDN GenericInformation (GI) parameterfor the PSAP's display equipment to convert to a street address. As ofearly 2002, the CGL parameter is not able to select the PSAP at thelocal exchange carrier's selective router, and commercial PSAP equipmentis typically not modified to convert an ISDN GI parameter to a streetaddress. In other words, CAS Phase II may not be an E911 option for manyyears into the future for many PSAPs due to the less than optimalnetworks and equipment used by the PSAPs.

In fact, for certain cases that apply to this invention, it may benecessary to substitute the ESRD used for call routing and setup, beforethe E911 call leaves the wireless switch, to overrule which PSAP that aselective router would otherwise choose based on the caller's servingsector ESRD, in order to ensure that the call will use an ESRD that willroute to the PSAP that is indicated by the caller's precise position!When this is needed, the correct ESRD that represents the caller'sserving cell sector can be presented to the PSAP's display equipmentover a Non-Call Associated Signaling (NCAS) path. NCAS is a viable E911option for Phase II given the constraints of less than optimal callsetup routing and PSAP equipment.

Since most PSAP equipment is not able to accept 20 digits and can onlyaccept 10 digits or even less, “ISUP loop-around” technology allows athird party vendor to assign a “key” that the PSAP can use. The industrycalls this key an ESRK. E911 calls that contain ESRKs are not subjectedto PSAP selection by ESRD at the local exchange carrier's selectiverouter. The ESRK is passed to the PSAP using the less than optimalavailable call routing and setup. The PSAP passes the ESRK back to thethird party over NCAS and this is used to retrieve the information.

ESRKs are assigned to a pool for each PSAP. Then, each successivewireless E911 call is assigned an ESRK from the pool that corresponds tothe PSAP indicated by the caller's serving cell sector or with Phase IItechnology, the pool that corresponds to the PSAP indicated by thecaller's precise location.

GSM wireless switches have demonstrated two deficiencies that “ISUPloop-around” technology is able to overcome the GSM wireless switchbeing only able to select the PSAP pool based on the caller's servingcell sector. The solution to these problems is not confined to “ISUPloop-around” technology. Rather, the same function can be accomplishedusing other messages. Regardless, what must occur is for the GSMwireless switch to delegate these decisions to a node outside of GSM anddeliver the caller's callback number and serving cell sector, e.g., viaISUP or TCAP technology to a third party's Mobile Position Center (MPC).Per the J-STD-036 standard, the GSM wireless switch will deliver a TCAPSubscriberLocationReport message that contains the caller's preciselocation to a GSM GMLC, which can be the same node as the MPC.

The outside node correctly selects the assigned PSAP based on thecaller's location or position by (1) marrying Phase I informationgleaned from the ISUP loop-around call setup message at an MPC; (2)modifying the ISUP loop-around technology to postpone the selection ofPSAP and hence selection of ESRK that will be used for the GSM E911 calluntil a configurable timer expires; or better, (3) having the Phase IIGSM TCAP location information arrive at the GMLC in time to influencethe MPC's ESRK selection. Thus, MPC implies ISUP side, whereas GMLCimplies GSM side.

If the TCAP location information does not arrive, the PSAP is selectedbased on the Phase I information. In either case, the ISUP loop-aroundor TCAP technology completes the call setup back to the GSM wirelessswitch, ultimately leading to egress out of GSM towards the PSAP.

When the call setup requires what the industry calls “Hybrid CAS”(HCAS), the ESRD and callback number form the key that replaces the needfor an ESRK. An ESRV can replace the need for an ESRD.

The outside node is preferably also able to manipulate the PSAPselection for HCAS. However, instead of choosing an ESRK from anindicated PSAP's pool, a known ESRD or ESRV that is associated with theindicated PSAP can be used for call setup routing to the PSAP. As notedabove, the local exchange carrier's selective router will use the ESRDto select a PSAP, and will be oblivious as to whether this ESRDrepresents the caller's serving cell sector or represents an ESRV thatcorresponds to the PSAP that is indicated by the caller's preciselocation.

Accordingly, it is most likely that a transfer between PSAPs has beenavoided when a call is answered by the PSAP indicated by the caller'sprecise location, when the PSAP is different from another PSAP indicatedby the E911 caller's serving cell sector.

Two main benefits to the present invention are 1) the ability for GSM tooffload the management of ESRK assignments; and 2) the ability to useprecise location information for wireless E911 calls to influence ESRKor ESRD or ESRV assignments, leading to better accuracy in PSAPselection and fewer PSAP transfers.

Furthermore, call setup routing to the local exchange carrier'sselective router is notoriously complex and not standard. By offloadingthe ESRK selection and hence the call setup routing that is ultimatelyrequired, the GSM wireless switch need only “tandem” an E911 call,rather than have to be configured to the myriad of parametercombinations that are currently in use. ISUP loop-around technologyappears as a “tandem” call, and thus everything is pre-configured sothat the GSM wireless switch merely passes thru what it receives fromthe outside node.

With the present invention, GSM wireless switches in North America canachieve parity with ANSI wireless switches where J-STD-036 has provideda protocol to accomplish “routing based on position” that does not relyon selective router technology.

While the present invention describes routing based on location withrespect to E911 applications, the present invention is equallyapplicable to non-E911 applications.

While the invention has been described with reference to the exemplaryembodiments thereof, those skilled in the art will be able to makevarious modifications to the described embodiments of the inventionwithout departing from the true spirit and scope of the invention.

1. A method of providing cross-carrier messaging, comprising:intercepting a short message from a sending subscriber of a firstwireless carrier intended for transmission over an Internet; storingsaid intercepted short message in an individual subscriber queue locatedin a gateway; determining a destination of said short message based on amobile identification number (MIN); and automatically delivering saidshort message to said receiving subscriber of a second wireless carrierdifferent from said first wireless carrier without transmission oversaid Internet; whereby said short message is transmitted betweendifferent wireless carriers without requiring transmission over anInternet. 2-10. (canceled)